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What Causes Sharp Knee Pain?

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Last updated December 20, 2022

Sharp knee pain quiz

Take a quiz to find out what's causing your pain.

The knee is the most stressed joint in the body and used in every movement—walking, jumping, running, even standing. Conditions and injuries that cause knee pain can affect people of all ages.

Sharp knee pain quiz

Take a quiz to find out what's causing your pain.

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What can cause sharp knee pain?

The knee is a complex system of bones, cartilage, ligaments, tendons, and muscles responsible for weight-bearing and movement. Anything that causes stress, inflammation, or injury to the knee can result in sharp knee pain.

Most people experience knee pain at some point in their lives. Older people may get knee pain and discomfort from multiple age-related conditions. Younger people may experience similar symptoms but the cause is more likely from playing sports or doing other physical activities.

Whatever the cause, sharp knee pain symptoms are often a sign of serious knee injury, and you should have it checked by a medical provider right away.

Knee pain symptoms

Whether the cause is from an age-related condition, overuse, or overtraining, the symptoms of sharp knee pain are often similar. A medical provider can help you figure out the cause and the best way to treat it.

Common symptoms with sharp knee pain

  • Swelling
  • Stiffness
  • Redness or warmth to the touch
  • Cannot fully extend or flex the knee
  • Cannot put weight on the knee
  • Sensation of instability or "giving out" of the knee
  • Popping noises when moving
  • Visible deformity

Common causes

Musculoskeletal or mechanical causes

Musculoskeletal causes of sharp knee pain may include the following:

  • Ligament: Ligament injury in the form of sprains and tears is very common in contact sports that also involve running, like in soccer, football, and rugby.
  • Cartilage: Tears of the knee cartilage is when the knee twists while weight-bearing and often happens during sports.
  • Fracture: The various bones of the knee can be broken in a car accident and from a serious fall. A trip or misstep is more likely to fracture a bone in older people or those with weak bones.
  • Mechanical: Problems with how the parts of the knee work together can result in sharp knee pain with movement.

Medical causes

Medical causes of sharp knee pain may include the following:

  • Arthritis: Arthritis is a general term for conditions that cause painful inflammation and stiffness of the bones and joints. When arthritis affects the bones and fluid-filled areas of the knee it can cause chronic and debilitating knee pain.
  • Infection: Scrapes and cuts on the knee make it easy for bacteria to get into the joints. These infections can cause serious swelling, pain, and redness of the knee.

Dislocated kneecap

The kneecap connects the muscles in the front of the thigh to the shinbone. When the kneecap slips out of the groove, it often causes problems and sharp pain.

A dislocated kneecap should be examined by a medical provider as soon as possible and no longer than within 24 hours. They may need to do a reduction, which is when the kneecap is pushed or popped back into place.


Fibromyalgia is a group of chronic symptoms that include ongoing fatigue, tenderness to the touch throughout the body, musculoskeletal pain, joint pain—especially in the knee and hip—and numbness and tingling in arms and legs. Dealing with these symptoms can also cause depression in many people.

While the cause is not known, fibromyalgia often starts after a stressful physical or emotional event, like an automobile accident. It may also involve a genetic component where a person experiences normal sensation as pain.

Almost 90% of people who have fibromyalgia are women.  If you have a rheumatic disease, like rheumatoid arthritis or lupus, or osteoarthritis, you may be more likely to develop fibromyalgia.

Difficulty sleeping is often a symptom, along with foggy thinking, headaches, painful menstrual periods, and increased sensitivity to heat, cold, bright lights, and loud noises.

Iliotibial (IT) band syndrome

The iliotibial band is a long, thick piece of connective tissue that begins at the top of the hip bone, runs down the outside of the leg, and attaches at the side of the knee. Iliotibial band syndrome is from overuse. Intense training can cause it, especially in runners and cyclists.

When the IT band constantly rubs against the outside of the knee joint, it causes pain and inflammation. Symptoms include pain on the outside of the knee, especially while running, going down stairs, or sitting with the knee flexed.

Jumper's knee (patellar tendonitis)

Jumper's knee is also called patellar tendonitis or patellar tendinopathy. It is an inflammation of the patellar tendon, which runs from the bottom of the patella (or kneecap) to the top of the shinbone.

It is most often an overuse injury seen in athletes, especially those in sports involving jumping, but it can affect anyone. Intense physical activity without warming up first, or tightness and inflexibility in the muscles of the thighs, can also put strain on the patellar tendon.

Symptoms include pain just below the kneecap and stiffness. Knee pain may get worse when going up stairs or squatting. At first, you may only notice pain when exercising, but it can become chronic as the tendon becomes more damaged and inflamed. Eventually the pain interferes with everyday movement.

Knee arthritis

Knee arthritis is when there is inflammation and damage to one or both of the two joints in the knee. Arthritis in any joint is most often caused by long-term wear and tear and called osteoarthritis. It can also be from rheumatoid arthritis, which is an autoimmune condition that attacks the joints. Post-traumatic arthritis is from an injury.

Knee arthritis symptoms include pain that becomes worse with use of the joint, limited range of motion,  swelling of the knee, instability, and stiffness, especially in the morning.

Knee bursitis (pes anserine bursitis)

Pes anserine bursae are small cushion-like structures inside of the knee, about two inches below the kneecap. Inflammation of these bursae is called pes anserine bursitis.

Knee bursitis can develop when there is pressure on the knee, like from kneeling and overuse. It can also be from an injury,  bacterial infection, or conditions like osteoarthritis, rheumatoid arthritis, or gout.  Symptoms include pain, tenderness, and swelling, especially when climbing stairs or exercising, and knee pain that gets worse when going up or down stairs and when standing up.

Meniscal injury

The menisci are the two pieces of cartilage between the lower end of the thigh bone and the top of the shinbone. It is also called "torn cartilage."

The meniscus is often damaged when there is a forceful, twisting movement or a direct hit to the knee. like when being tackled. Older people may tear a meniscus when doing everyday  activity if the cartilage has become thin and worn from getting older.

Symptoms include pain, stiffness, and swelling. The knee may not seem to be working correctly and may catch, lock up, or give way.

Patellofemoral pain syndrome

Patellofemoral pain syndrome (PFPS) is also called runner's knee, anterior knee pain, chondromalacia patella, and patellofemoral joint syndrome. It is most common in females and young adults who are active in sports. Overuse when training for sports wears away the cartilage beneath the kneecap and causes pain when exercising.

Symptoms include dull pain at the front of the knee and around the kneecap (patella) while running, squatting, or climbing stairs, or after sitting with knees bent. Surgery is needed only for severe cases.

Prepatellar and infrapatellar bursitis

Bursitis is an inflammation of a fluid-filled sac (bursa) that normally acts as a cushion to help reduce friction.

Prepatellar bursitis is bursitis in the front of the knee (prepatellar). Infrapatellar bursitis is an inflammation of the bursa beneath the kneecap (patella).  Infrapatellar bursitis is also known as housemaid's knee, clergyman's knee, parson's knee, and vicar's knee.

Both prepatellar bursitis and infrapatellar bursitis can be caused by prolonged kneeling,  especially on hard surfaces. Other causes of these two types of bursitis are hemorrhage, infection, traumatic injury, or inflammatory diseases like arthropathy.

Bursitis can be acute or chronic. When acute, symptoms include warmth, redness, swelling, and pain at the front of the knee (prepatellar) or below the kneecap (infrapatellar). If there is a cut near the knee or you have a fever, the bursa may be infected. When prepatellar bursitis is chronic, you may notice a soft, painless lump at the front of the knee.

Treatments for knee pain

When to see a doctor

If you have severe knee pain, you should get medical attention right away. Treatment is based on the specific diagnosis and may include one or all of the following:

  • Physical therapy: After many knee injuries, your provider will suggest physical therapy to restore range of motion, strength, and stability to your knee.
  • Medication: If your severe knee pain is from an inflammatory condition, your doctor may prescribe antibiotics to treat an infection or anti-inflammatory medications to treat arthritic conditions.
  • Surgery: Fractures and tears of the ligaments and cartilage of the knee often need surgery. It is often very successful.


There are many changes you can make to help prevent knee injury and severe pain, including:

  • Maintain a healthy weight. The knees bear all of the body's weight, so extra pounds can cause unnecessary stress and strain, increasing risk of injury.
  • Be strong and flexible. The quadriceps and hamstring muscles help support the knee joint, so keeping them strong, conditioned, and flexible helps the overall functioning of the knee.
  • Practice technique: If you participate in competitive sports and practice often, you want to make sure that your techniques and movements are not putting unnecessary stress on your knees. Consider working with a coach to ensure that when you run, jump or move side-to-side, your knee is in the best position to prevent injury.
  • Listen to your body. If you find yourself experiencing mild or transient knee pain after certain activities, listen to your body and take a break. Rest, ice, and elevate your knee immediately after feeling sharp knee pain symptoms and make an appointment with a medical provider right away.

Questions your doctor may ask you about your knee pain

  • Do you have knee pain in one or both knees?
  • Where in the knee do you feel the pain?
  • What do you think is causing your knee pain—does it happen after certain activities?
  • Do you often feel like your knees are buckling?
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The stories shared below are not written by Buoy employees. Buoy does not endorse any of the information in these stories. Whenever you have questions or concerns about a medical condition, you should always contact your doctor or a healthcare provider.
Dr. Rothschild has been a faculty member at Brigham and Women’s Hospital where he is an Associate Professor of Medicine at Harvard Medical School. He currently practices as a hospitalist at Newton Wellesley Hospital. In 1978, Dr. Rothschild received his MD at the Medical College of Wisconsin and trained in internal medicine followed by a fellowship in critical care medicine. He also received an MP...
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